‘How are we to be confident’? Sharyl Attkisson makes THE point regarding the FBI’s woes in finding ‘real risks’

Investigative journalist Sharyl Attkisson makes a really thought-provoking point regarding the manner in which the FBI and other law enforcement agencies identify who is a threat.

Another shooter who was on FBI (and Secret Service) radar prior to the shooting. If we can't figure out who the real risks are and monitor them when they literally cross law enforcement's path, how are we to be confident all this secret surveillance nets much?